The objective of the Environmental Toxicology and Epidemiology Program (ETEP) is to train future leaders in environmental health sciences (EHS) who accelerate improvements in public health. This program is based on the premise that transformative research in EHS requires scientists with specialized knowledge who engage in multidisciplinary research. This program focuses on translational applications to human disease prevention with training that bridges environmental mechanistic toxicology (basic research) and molecular epidemiology (population-based research) (i.e., T3 translational research). The investigators' focus emphasizes the application of molecular tools such as biomarkers of toxicant exposure/response, genomics, epigenomics, metabolomics, proteomics, and transcriptomics to conduct mechanistically-oriented research in laboratory models and human populations. The proposed training continues their highly successful program, moving into our 32nd year of NIEHS support. Pre-doctoral trainees specialize in environmental epidemiology or mechanistic toxicology, and take a foundation course and an advanced course in the non-specialization area (i.e., epidemiology trainees take toxicology courses and vice versa). In addition, there is a common core curriculum that consists of a bioinformatics course and a course in professional communication and development. The investigators request 8 pre-doctoral and 3 postdoctoral positions (at levels 0, 1 and 2) in this submission, increased from 6 pre-doctoral fellowships and continuing 3 postdoctoral fellowships from the last cycle. The expected duration of trainee support on this training grant is two years, though the expected total duration of pre-doctoral training is 4-5 years. Pre-doctoral and postdoctoral trainees will be encouraged to submit Individual NRSA Fellowship applications (F31 or F32, respectively). Alternatively, postdoctoral trainees may be encouraged to submit K99/R00 application. Qualified applicants must demonstrate motivation for careers in EHS mechanistic toxicology or mechanistically-oriented epidemiology research. Pre-doctoral trainees must have a baccalaureate degree with relevant scientific coursework preparation and will be enrolled in a Ph.D. program in the Department of Environmental Health Sciences, which has a distinguished history of graduate training in toxicology. Postdoctoral fellows must have the Ph.D., M.D., DVM, or other appropriate doctoral degree. The program addresses most of the themes and strategic goals of the NIHES 2012-2017 Strategic Plan, and aims to advance the mission of the NIEHS to discover how the environment affects people in order to promote healthier lives.